check_availability

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the burden. It clarifies this is a read/status operation and implies it does NOT mutate state, which is helpful given no readOnlyHint annotation exists. However, it doesn't describe the output format or whether the tool errors on unknown ISBNs. For a simple read tool with a clearly implied non-destructive nature, this is acceptable though not rich.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact—two sentences total—with the purpose front-loaded in the first sentence and usage guidance in the second. Every sentence earns its place with zero filler or redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description is complete for a simple single-parameter read tool. It provides purpose, usage context, and preconditions. The presence of an output schema (presumably with availability counts) means return value explanation isn't necessary. Sibling context makes the differentiation clear. Only minor optional enrichment (e.g., whether 'available copies' includes held items) would push it higher.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% for the single 'isbn' parameter, so the schema already documents it fully as 'The ISBN of the book to check.' The description reinforces that ISBN is a prerequisite ('already has an ISBN') but adds little beyond the schema. Baseline 3 is appropriate since the schema does the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb+resource ('Check how many copies... are available to borrow') and clearly identifies the scope (stock availability for a specific book). It distinguishes itself from siblings by focusing on availability checking versus borrowing (borrow_book) or searching (search_books).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly states when to use: 'when the user already has an ISBN and wants to know stock levels before attempting to borrow, or just want a quick status check.' This provides clear context and helps the agent distinguish from when to use borrow_book or search_books.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.